Electrochemical cells in the form of batteries are conventionally used to power many types of electronic devices, and are available in several forms, including, for example, cylindrical, button, pouch and prismatic cells. In some cases, electrochemical cells and methods of making cells for use in an implantable medical device (IMD) can be designed in a compact configuration, such that an IMD can be readily implanted in small spaces within a patient's anatomy. As such IMDs are required to be smaller for various medical applications, new challenges in manufacturing of the components for the IMDs, such as batteries, present themselves. One such IMD is a pacemaker. In one example, a leadless pacemaker can be implanted directly within the heart, attached to an interior wall of a heart chamber, and incorporate both a battery and electronics for providing stimulus to the heart. Such an IMD eliminates the need for leads used in conjunction with conventional pacemakers, which typically run from a pacemaker implanted external to the heart to positions within heart.
To provide a pacemaker that can be implanted within a heart chamber, the size of the pacemaker is reduced to a volume that can not only fit inside the heart chamber, but which is sufficiently small so as not to significantly interfere with the heart operations in terms of expansion and contraction, and blood flow through the heart. Still further, the pacemaker should be capable of operation over a period years such that the battery provides sufficient energy storage for such operation yet remain within the size constraints dictated by intra-heart operation.
In one example, battery energy storage is directly related to the volume of the anode and cathode electrodes, which react via an electrolyte fluid. Aside from improvements in electrochemical cell materials that could provide greater energy density, the size of the battery is typically dictated by energy requirements with the remaining volume dictated by packaging requirements. As such, packaging requirements for such an IMD can be stringent and include proper sealing over a lifetime of such a battery.
One exemplary consideration of such IMDs is size requirements, which can include the size of a feedthrough conductor that can be reduced resulting in a conductor that is delicate and connected to IMD components with care. This design can be employed to avoid excessive displacement of the conductor, which can lead to electrical shorting. Accordingly, error tolerances in making connections to such a feedthrough conductor of the battery are commensurately stringent and may require multiple tooling operations to make such connections. This disclosure describes an improvement over these prior technologies.